A Multimodal Intravital Molecular Imaging System based on Dorsal Skin Window Chamber Tumor Model

Objectives As the development of intravital imaging, complementary information is demanded to understand complex tumor microenvironment [1-3]. This study established a multimodal intravital molecular imaging system, which can acquire direct positron imaging, conventional and hyperpolarized MRI, luminescence sensor imaging as well as routine optical imaging.

Methods The multimodal intravital molecular imaging is established based on a dorsal skin window chamber tumor model on RNU nude rat. The chamber was designed for imaging and co-registration of data from a Medipix positron detector, MRI, luminescence sensor and fluorescence microscope. To test the system, cell line HT-29 was injected into the window area 3 days after chamber preparation. Two weeks after tumor transplantation, 30MBq [18F]FDG was injected into the rat and positron imaging was scanned 1h p.i. for 1.5 min. Hyperpolarized 13C-pyrutate imaging was scanned (resolution 2.5 mm) directly after injection of 13C-pyrutate. Afterwards, conventional T1 and T2 MR imaging was done. A luminescence sensor was tested for the imaging of oxygen gradients. Fluorescence imaging was acquired after injection of FITC-Dextran. The images of different modalities were co-registered with fiducial references.

Results For the first time, positron imaging, hyperpolarized MRI, luminescence sensor, and fluorescence imaging were integrated together for the same living animal. From the initial results, more lactate production is observed on hypoxia area and high FDG uptake is surround hypoxia.

Conclusions The preliminary test demonstrates the feasibility of the multimodal intravital molecular imaging for the investigation of tumor microenvironment. The proposed system offers the opportunity to explore dynamic and longitudinal multimodal imaging. The resolution of hyperpolarized MRI is under further improvement.